Machine Fixes That Made Me Go 'DUH!'

Manufacturing engineer Jeremy Cook discusses a few machine failure problems that seemed complicated at the onset, but were quite simple to solve in the end, and the lessons he learned.

As you can see in my bio at the end of this article, I work as a manufacturing engineer. One of my favorite things that happens on a Friday late in the afternoon is to hear my phone ring and see the number of a technician come up: I just know he's going to inform me that a machine has just undergone some kind of catastrophic failure.

OK, maybe it's not my favorite thing to do, but if our jobs were fun all the time, we'd probably be working for free.

Although I've learned (hopefully) to appear outwardly patient and in control, at the back of my mind is the constant nagging fear that I will literally never be able to go home because I can't figure out what's going on. Or maybe I have now run into the one problem that finally can't be solved, and I'll get fired.

The good news is that I've always made it home (so far) and in some cases I've even made it home on time. What follows are a few problems that seemed complicated at the onset, but were quite simple to solve in the end, and the lessons I learned.

Case 1: Recently, I was called out to look at a machine because the vision system was working correctly, but the display was not. The technician who immediately serviced it said he checked the wires and cycled the VGA monitor off and on to no avail. Fortunately, I'd seen this before and, seeing the male side of a VGA cable lying on the floor, soon found its mate. I then stuffed it further into the machine where it would hopefully not get knocked out again.

Lesson: Make sure everything is plugged in!

Case 2: Another machine kept faulting out because a pneumatic cylinder was supposedly not in the correct position. The technicians claimed the sensors were working correctly, but after maintenance changed out a drive motor, things still didn't function correctly.

Our electrical engineer hooked up to the PLC with a computer, and after I manually manipulated the cylinder that we suspected the problem was coming from, all the sensors appeared to check out. Actually, there was one sensor that seemed to have some issue going on, but after adjusting the position, it appeared to work. I initially asked the tech to get more of these sensors but, after seeing it working correctly, decided this wasn't necessary.

After trying to troubleshoot this machine for another hour or so, I saw this sensor again not come on. We then changed it out and found the original sensor with frayed insulation at several points. The machine then performed as it should.

Lesson: Sometimes you should trust your gut, especially when it's easy to follow!

Case 3: Working with the same electrical engineer from the “Catastrophe!” before, we had a small touch panel that needed to be replaced. He loaded the program on, but unfortunately, we kept getting the message “Over Reject Limit.” The touch screen didn't seem to work correctly at all and wouldn't let us reset the counter. Then -- after quite a bit of troubleshooting -- I happened to swipe my finger across the screen in a way that made the screen change. Maybe the display wasn't set up correctly?

This particular touch screen had an option to calibrate the display. Naturally, we'd ignored it. Obviously, the problem was more complicated than that. Well, it wasn't. After running the calibration routine, the machine was able to reset correctly.

Lesson: If there's an option to calibrate equipment, it's probably there for a reason!

If you're ever in this situation (as undoubtedly most of our readers are from time to time), don't forget to check the simple fixes first. If that doesn't work, move on to the next set. I'll write about attacking those situations in my next blog.

— Jeremy Cook is a manufacturing engineer with 10 years' experience and has a BSME from Clemson University. You can find him on Twitter at

Enabling the customer to save face is brilliant - and probably accelerates the solution! My high schoo,l teacher used to find that errors in complex mathematical problems were usually trivial addition errors. His mantra was" Higher mathematics is never sufficient, one must be able to add and subtract". I suppose in electrical engineering, we might say "Follow the wire connections from end to end".

Been there... Doing some commissioning work on a OEM/customers site , ~ 2hr flight away. Everything would be setup up correctly, PID's all tweaked, decide to push some product through and some little niggly thing pops up ......

Get to 5:30pm and it's not quite working, frantically change the airline booking online , ring the wife, book a motel. Sometimes this would happen three days in a row! Motel is now on speed dial.

wrt to your examples:

Case1: And plugged into the correct connector! e.g. using the correct one when 2 com ports are available. And with USB ports, moving the serial dongle to another port (this changes the assigned COM port in Windows on the laptop that was being temporarily used to replace a broken HMI) . One machine has dual encoders at inlet and outlet of machine, the controller switches from one to othe r based on some algorithm, easy enough to swap the encoder plugs over, but one calibration is slightly different to other. Difficult to tell it's swapped over until the rare occasions when they attempt a roll change mid-job , then it gets really weird, (this might happen weeks after the original swapover).

Case 2: Hydraulic cylinders on left and right side, both always operate together , each has proximity switches. On about half the machines made the proximities were on the wrong cylinders, but you can't tell because they both move together, until one day when one cylinder jammed on a machine, resulting in really confusing diagnostic and self-test information from the controller, so they pull off the (wrong) cylinder - nothing wrong with it , put it back on - still faulty .... eventually they worked it out .

Case 3: Calibration menu: How about the operator stumbling into the calibration screen and pressing OK to exit rather than cancel, this then loads some default values and some zero's

Case 3: Operator does a calibration, but inadvertently loads the wrong calibration file. (they should just use the existing file, but you know how they are... and they deny everything..)

Case 3: frantic Phone call/email from operator: lengths seem to be inaccurate and getting slowly worse over several days,doing a calibrate didn't fix it. My reply: check the encoder wheel and coupling, and the spring (these cal errors are almost always related to encoder mechanical issues) . Frantic phone call second day , gave them the same advice, explaining in some detail where to find the appropriate screws to tighten. Then silence for a week, I gave them a courtesy call, and they said the encoder wheel fell off on the third day, and, after re-attaching it , everything worked perfectly.

One job of mine involved a lot of report writing for a database system installed in a large semiconductor company. In addition to writing the reports, I often had to field calls from users when things were not going well.

I can't count the number of times when the answer to a frantic call reporting "The system has bugs and it crashed" was "Turn... the printer... on"

I had a similar experience many years back involving a new dishwasher. My husband and I had just redone our kitchen and ordered new appliances in a matching almond color (this was before stainless steel became all the rage). The dishwasher was delivered and installed, and we realized that the front panel was white, it did not match the other appliances! We were freaked out, to say the least, and I had one hand on the phone ready to dial up Sears when my husband realized that the front panel could be slid out. Behind it were two other panels, in avocado and almond. So we were all set for all contingencies!

I had a similar experience with my first (and so far only) smartphone, but mine had to do with the camera. I could get good -- not great, but decent -- pictures with it sometimes, but any time the flash went off my pictures were horrible. After fumbling with the flash and camera settings for a bit, I had finally resigned myself to taking the phone back to the store when I noticed that one corner of the screen had a peculiar mark on it.

Upon checking further, I realized that the "mark" was where a bit of protective film had been roughed up a little. It turns out that when the salesman unboxed the phone in the store and put it into its case, he had neglected to remove the film. Every time the flash went off, the light was diffused through the film, which also covered the camera lens. Removing the film fixed the problem and saved me a little face.

Reminds me of a TV repairman story. Seems the picture suddenly became snowy, as the repairman was walking to the customer's door he glanced up at the antenna. There were several birds perched on it.

He told the customer the problem was possibly all those birds. Then he pulled the set away from the wall and noticed one wire of the twin-lead from the antenna had come loose (a fairly common problem). He re-attached the wire and got a nice picture. Meanwhile the customer had disappeared.

Suddenly he heard a loud BANG! The customer walked back in with a smoking shotgun and said "Got them pesky birds! Did that fix it?"